FBI agents are not paid in hourly wages, they are paid through the federal government system GS ratings which provides agents an annual salary rating for years served.
The tariff of the United States, like all actual protective tariffs, is partly revenue and partly protective, its original purpose of yielding revenue having been subordinated to that of giving protection, until it may now be best described as a protective tariff yielding incidental revenue.
The other purpose of a use tax is to help recoup the cost of public services directly related to the use of certain types of personal property.